Problem: 3 rubber stamps cost $3.36. Which equation would help determine the cost of 14 rubber stamps?
There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 3 rubber stamps cost $3.36 as a proportion: $\dfrac{3}{\$3.36}$ Let $x$ represent the unknown cost of 14 rubber stamps. Since 14 rubber stamps cost $x$ , we have the following proportion: $\dfrac{14}{x}$ The cost changes along with the number of rubber stamps purchased, and so the two proportions are equivalent. $\dfrac{3}{\$3.36} = \dfrac{14}{x}$